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#11
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Could we do a moon mission today?
I still have to ask why when -- if we absolutely have
to -- we may be able to do it in _two_ (lander first, C&SM/TLI stage after it). (?) Well we did the moon an a single launch. Saturn 5. But if we were preparing to go to mars a single launch would be tough and so large it would never have another use We put ISS up in pieces, so some assembly required can be done. I just asked if it could be viable for the moon and eventually Mars? Besides I hope it would get some nice discussion going |
#12
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Could we do a moon mission today?
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#13
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Could we do a moon mission today?
In article ,
Herb Schaltegger wrote: I may be wrong, but it seems to me that the amount of energy needed to brake from a lunar return velocity to the velocity of the ISS orbit makes a direct return to earth much more feasible... Furthermore, to transition to the orbital inclination of the ISS (instead of roughly equatorial) and actually rendezvous with it would seem to complicate the mission needlessly. You do the inclination change as part of the lunar departure burn; it costs almost nothing then. Provided, that is, that you can pick a departure time when the Moon is roughly in the plane of ISS's orbit. But a rendezvous is definitely a significant added complication. -- MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer first ground-station pass 1651, all nominal! | |
#14
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Could we do a moon mission today?
In article ,
Francis Marion wrote: I got the impression the original poster was asking about existing technology. I assumed he/she meant with existing hardware? We don't have existing hardware other than the shuttle to do manned re-entry's with do we? We don't have most of the hardware that would be needed for this. It will inevitably mean building new hardware. -- MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer first ground-station pass 1651, all nominal! | |
#15
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Could we do a moon mission today?
In article WtgRa.79402$Ph3.7994@sccrnsc04,
Francis Marion wrote: We might be able to send a person or two on a quick sling shot type of mission. If you just want to go around the Moon on a free-return trajectory -- no landing, no orbit -- that could probably be done fairly quickly, modifying a Soyuz to something approximating the old Zond configuration and launching it on a Proton. Anything much beyond that is going to require new launchers, orbital assembly, or both. -- MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer first ground-station pass 1651, all nominal! | |
#17
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Could we do a moon mission today?
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#18
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Could we do a moon mission today?
"Louis Scheffer" wrote in message ... (Henry Spencer) writes: In article , Rick DeNatale wrote: Most likely the return would be to the ISS, with ultimate Earth return in a US or Russian vehicle. I may be wrong, but it seems to me that the amount of energy needed to brake from a lunar return velocity to the velocity of the ISS orbit makes a direct return to earth much more feasible. Correct. It is a *whole lot* cheaper, in both mass and complexity, to include a heatshield than to include the necessary braking fuel. It's true you need a heatshield, because of the radiation problem, but The heatshield is there to solve the thermal problem. it's not obvious to me that capture into orbit is more massive. You need a restartable engine and quite a large amount of fuel. It *will* be heavier. The Apollo heat shield was quite heavy. Perhaps you could use a lighter Not as heavy as an additional stage. heatshield (perhaps derived from shuttle technology, so it's non-ablative) The shuttle's tiles aren't designed for a high-energy reentry from a lunar return trajectory. JCS |
#19
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Could we do a moon mission today?
"James Stutts" writes:
[From Henry Spencer:] Correct. It is a *whole lot* cheaper, in both mass and complexity, to include a heatshield than to include the necessary braking fuel. It's true you need a heatshield, because of the radiation problem, but The heatshield is there to solve the thermal problem. Not in this case. You could do aerobraking with no additional mass, as planetary probes do, but you'd go through the Van Allen belts too many times since the process is gradual (plus problems with consumables, of course) So the heat shield is there so you can take off more velocty with each pass, and hence avoid the radiation problem. it's not obvious to me that capture into orbit is more massive. You need a restartable engine and quite a large amount of fuel. It *will* be heavier. As I said, this is not so obvious. From a previous posting of mine: A quick back-of-the-envelope calculation indicates that aerocapture could be worth while from a mass point of view (of course it's adding lots of complexity and failure modes). The command module heat shield was quite heavy - 848 kg. If we just reduce speed to orbital that's about 1/2 the energy, so I'd guess that means a heat shield of 1/2 the weight, so we save 420 kg. Of course, you do need to circularize the orbit, but this can probably be done with existing thrusters and some extra fuel: Shuttle re-entry and circularization burns are about 80 meters/sec delta-V. RCS thrusters on the command module had an exhaust velocity of about 2840 m/s. So we need about 3% of the command module mass to circularize, or about 150 kg. So at first glance the net savings are about 280 kg. The Apollo heat shield was quite heavy. Perhaps you could use a lighter Not as heavy as an additional stage. True, but there is no need for an additional stage. See above. heatshield (perhaps derived from shuttle technology, so it's non-ablative) The shuttle's tiles aren't designed for a high-energy reentry from a lunar return trajectory. Lunar return to Earth orbit is roughly equvalent, energy wise, to earth orbit to the ground. Plus there's the possibility of doing it in several passes, allowing the heat shield to cool in between. Lou Scheffer |
#20
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Could we do a moon mission today?
In article , president@the-
dma.org says... snip Huh. Good point. As I often mention when prefacing posts in "what-if" threads, "IANAE" (I Am Not An Engineer). Perhaps what we really need at this point is an old astronaut lurking who chimes in on whether or not it'd be easier to launch the LM first and then have to chase it, or be already waiting in orbit when it shows up. Just how long _did_ it take those Gemini crews to catch up with the Agena when it came time to give chase, anyway...like, five or six hours into it? It depends on which Gemini flight you're talking about. The first few rendezvous missions used a four-orbit rendezvous profile (roughly six hours from launch to stationkeeping). A three-orbit profile was also used in later missions, and Gemini XI proved the first-orbit rendezvous technique ("Would you believe, M equals one?"). The first two lunar landings used the three-orbit technique, and all the later ones (14 through 17) used a first-orbit rendezvous. What I would find interesting would be the mission plan for the AS- 205/208 (or, more simplified, AS258) mission that was almost flown. This was to be the first checkout flight of the LM, with the McDivitt-Scott- Schweickart crew. At the time of the Fire, AS258 was originally planned to be the second manned Apollo flight, featuring the first flight of a Block II CSM and the first manned flight of a LM. Since the Saturn V was not scheduled to be ready yet, the CSM and LM were scheduled to be launched on separate Saturn IB boosters (hence the 205/208 designation). It would be interesting to see whether the CSM or LM was scheduled to be launched first. I'd be tempted to believe the CSM would be launched first, since the S-IVB stage has a limited orbital lifetime and I'm pretty certain they planned on performing the docking and extraction while the LM was still attached, to most closely simulate the maneuvers to be used on lunar flights. -- It's not the pace of life I mind; | Doug Van Dorn it's the sudden stop at the end... | |
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